divergence.py

import math
import sys

class HarmonicGenerator(object):
    """docstring for HarmonicGenerator"""
    def __init__(self):
        super(HarmonicGenerator, self).__init__()
        self.n = 0

    def __next__(self):
        return self.next()

    def next(self):
        self.n = self.n + 1
        result = 1.0/self.n
        return result

    def __iter__(self):
        return self


def compute(target, precision):
    pos = HarmonicGenerator()
    neg = HarmonicGenerator()
    acc = 0

    for x in pos:
        acc = acc + x
        if acc > target:
            val = neg.next()
            acc = acc - val
        elif math.fabs(acc - target) < precision:
            break

    print 'Computed   :', acc
    print 'Actual     :', math.pi
    print 'Iterations :', pos.n
    print 'Negative   :', neg.n

def main():
    args = sys.argv[1:]
    target = int(args[0])
    precision = float(args[1])

    compute(target, precision)
    
if __name__ == '__main__':
    main()